The present invention relates generally to a control system for fuel supply to an internal combustion engine. More specifically, the present invention relates to a fuel supply control system which determines a basic fuel amount to be supplied to the internal combustion engine and corrects the basic fuel amount to corresponding to engine load conditions.
Recently, there have been developed various control systems for controlling the fuel supply to an internal combustion engine such as, for example, a reciprocating combustion engine mounted on an automotive vehicle. Such a control system is extremely important to maximize efficiency and fuel economy and minimize the emission from the engine of noxious pollutants. For accomplishing these requirements, recent control systems for fuel supply include the operation of shutting off the fuel supply while the vehicle is decelerating. For shutting off the fuel supply in response to deceleration of the vehicle, it is necessary to detect a decelerating condition of the vehicle effectively and satisfactorily. In a conventional control system, deceleration or acceleration of the vehicle have been determined by detecting the closing or opening of a throttle valve provided in an air intake passage, the throttle valve being mechanically connected to an accelerator pedal so as to be incorporated therewith. For detecting the closing or opening of the throttle valve, a throttle angle sensor or accelerator pedal switch has been employed in the control system. The throttle angle sensor generates a sensor signal when the throttle valve is in the fully closed position. The accelerator pedal switch also generates a signal when the accelerator pedal is in the fully released position. For detecting accelerating and decelerating conditions of the vehicle accurately, the throttle angle switch and the accelerator pedal switch are required to work correctly and accurately.
The point where the throttle valve moves from the fully closed position to an opened position is quite delicate and is apt to vary from one vehicle to another according to the exact position in which the engine is mounted. The throttle valve is determined as opened when it has rotated 1 or 2 degrees from the fully closed position. In other words when the accelerator pedal is just slightly applied. Thus, it is necessary to adjust the throttle angle switch or the accelerator pedal switch after assembly into the vehicle so that it may operate exactly and effectively to detect the fully closed position of the throttle valve and thereby detect decelerating conditions of the vehicle and generate a signal in response to deceleration of the vehicle. This adjusting operation after assembly of the vehicle is quite troublesome and also increases the number of operations in the assembly operation for the vehicle which results in a lower efficiency of manufacture of the vehicle. Further, the mechanical parts of the sensor or switch are liable to breakage or wear by repeatedly being brought into contact and then separated. This may cause displacement of the switching point and also mis-contacting between the switch elements to result in malfunctions of the control system. To avoid such a possibility, it is necessary to check the system, particularly the switch or sensor, at regular intervals.
Furthermore, since the conventional system detects the decelerating and accelerating conditions of the vehicle by detecting whether the throttle angle switch or accelerator pedal switch is on or off, it is impossible to accurately and effectively respond to engine driving conditions. Particularly, conventional control system can distinguish only whether the engine driving condition is adapted to fuel supply shut off, and are not adapted to correct the fuel supply amount corresponding to the vehicle driving condition; i.e., decreasing the fuel amount under decelerating conditions of the vehicle and increasing of the fuel amount under vehicle accelerating conditions.
Moreover, it will be beneficial and economical if the decelerating and accelerating conditions of the vehicle can be detected without using the above-mentioned throttle angle switch or accelerator pedal switch; will make manufacture of a vehicle including such a fuel supply control system easier. Also, it will increase efficiency and accuracy of the control system if the detecting means for detecting the deceleration and acceleration of the vehicle does not use elements requiring high accuracy or delicate adjustment for assembly.